Many imaging devices, such as printers, photocopiers, and multi-function imaging devices, store a supply of media sheets, such as paper sheets, in one or more internal trays. The sheets are vertically stacked within the trays by a user or service technician. Media trays are sized and configured to hold hundreds or thousands of sheets.
Some imaging devices extract media sheets from a stack in the media tray starting from the top sheet in the stack. A media feeder uses various moving members, such as rollers, to extract the top sheet from the stack as needed to supply the imaging device. As sheets are removed from the stack, a lift plate positioned under the stack of sheets raises the remaining sheets in the tray so the top sheet in the media feeder remains ready for removal from the stack. In some printers, an electric motor raises the lift plate and media stack as the media feeder extracts sheets from the media stack.
In a tandem media supply configuration, a single media supply tray holds two stacks of media sheets that are positioned next to each other. One of the stacks is placed on the lift plate, while the second stack is held in reserve. When the media feeder extracts all of the media sheets from the stack on the lift plate, an actuator returns the lift plate to an area adjacent to the reserve stack so another actuator can slide the reserve stack of media sheets onto the lift plate.
Tandem paper supplies efficiently use space within an imaging device and enable the media supply to store larger quantities of media sheets than comparable trays that hold only a single stack. The tandem media trays are, however, typically more mechanically complex since a tandem media tray moves two different media stacks in different directions during operation. Existing tandem media supplies either use three separate electric motors to move the media stacks and feed media, or use two motors with a series of electromagnetic clutches to move the media stacks and feed media. The existing media supplies consume electricity during operation, and complex mechanical assemblies can suffer from reliability issues during operation. Improved tandem media supplies that supply media sheets to the imaging device with better reliability and lower energy usage would be beneficial.